Stroked 390?

[Power Surge]

Hey Keith, Sal here. Can you stroke a 390? I was thinking since the Scat cranks are so inexpensive, why not bump up the cubes using the 390 block? Can it be done? What kind of specs do we use for bore and stroke and what kind of CID can we get using a 390 block?

Thanks!

[blykins]

Sal,

It's pretty common to stroke a 390....

You have several Scat stroker cranks available.....a 3.98" stroke, 4.125", and 4.25".

Basing everything on a .030" overbore 390, you can get 416ci, 431ci, or 444ci.


Now if you stumble across a 390 block that's thick in the cylinders, you could increase the cubic inches a little more by opening the bores up .080" over.

If you start using a smaller bore and a real long stroke, I think you'll find that you'll get lots of torque, but your power curves are going to be at substantially lower rpm's than a big bore, short stroke engine.

[xlr8or]

Sal,
A standard 428 crank will give you 410 CI with a 390 block.

[John A. Simpson]

HI Sal, Have you looked on Keith's web site? His stroked 390s look like a great bargain with good power.

http://www.keithcraft.com/our_engines.html

Are you still interested in swapping wiring harnesses? I haven't worked on my car for about 2 months so I don't have pics of my harness yet.

[Power Surge]

Thanks for the link John. And YES, I would still like to swap harnesses.

Does anyone know what rod configuration I'd need to run with a stroker crank?

[John A. Simpson]

I believe a standard big block chevy is what works with the Scat cranks, also scat has BB chevy style rods available.

[Keithc8]

I have wondered why more of the Cobra guys don't consider this option because it give you the original FE looks at a much cheaper price than the 427 engine. I like the 4.125 and 4.250 strokes because I like the BBC 2.200 rod journal size and using the 6.700 long rod. We did one customer a 430C.I. 390 and it worked great. I would try to come up with some real reasonable turn key, dynoed 390 stroker engine if we could get some interest in several of them. The engine we did made about 540HP with our Edelbrock stage 2 heads and hydraulic roller. I wonder if we came up with some package that was 8995.00 to 9995.00 complete of the dyno if we would get much interest.
I also came across some 65 and earlier 390 blocks and got them because I thought someone might need a 65 and earlier block in CA and some other states.
I see no problem with the stroke being bigger than the bore since all we want to do is make power to about 6000rpms. Let me know if we need to put one of these together for you. Hell we can even install some bolts in the side that look like cross bolts. I guess we could start installing cross bolt caps on some of these blocks if that is what people want. Thanks, Keith Craft

[ZOERA-SC7XX]

I just had my '66 390 block done up .080 over with 428 std Keith Black pistons and a 428 crankshaft turned .010/.010 (which will make 428 cu. in.) with a Comp Cams Magnum 270H and a set of 69cc heads. It'll make 10.0:1 comp and should work very well in my 2600 lb. ERA. If you're on a budget and don't plan to twist it past 6000 rpm's, this may be the answer. Good luck.

[GunrunnerI]

Hi Sal,
this is a previous post from a friend of mine that has built what you are talking about. Hope it helps.

S-

Receipe for a mild/hot 390

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later (or any) 390 block that will pass a sonic check to allow .075" overbore. I have sonic checked dozens of 390 blocks that will go .075".
install main studs
oil mods to block
off the shelf Ross 4.125" forged pistons (Doug at Precision Oil Pumps can get them, and all the other parts you need for a good price.) 9.9 to 1 to 10.1 to 1 compression
Scat 4.125" stroke crank BBChevy rod journals
Scat 6.700" Rods BBChevy rod journals
Speed Pro or Sealed Power moly rings for a 400 Chevy (4.125")
Hydraulic cam around 240 degree duration @.050", .570" to .580" lift, 110 lobe centers.
If you really want to rev the crap out of it
run a mechanical flat tappet with 255 to 260 deg @.050"
.620 or so lift should get you to 6200/6400 rpm.
If you want more, buy a 427
good roller rocker arm set (Erson, Crane, Precision Oil Pumps, Harland Sharp, etc.)
Stage II ported Edelbrock heads (upgrade the valve springs)
Performer RPM intake
750 to 850 Holley Vacuum or DP
MSD billet Dist with timing set at 14 to 18 initial, 36 total.
442 cubic inches
idles at 850 rpm
runs great on pump gas
450 to 480 hp at 5800 rpm
Should be able to build this combo for 7 to 9 grand depending on who does the work.

[dlowman]

Keith,
Are you still thinking about offering a 390 block like this? Can you still do it for that price?

Thanks,
Dan

[Keithc8]

We can still do this for you and we have already done several stroker 390 block engines. I have a great deal right now on a stroker with a 428 blck and it only runs about 500.00 more. It will give you about 463C.I. with a 4.250 stroke and 4.165 bore. Just let me know how we can and what you would like for power and what budget you have. We deliver the best FE packages for the HP and cost going. Thanks, Keith